Ntt technical Review, July 2009, Vol. 7, No

Vol. 7 No. 7 July 2009
22
address of the attack target, denial-of-service (DoS) 
attack exploiting replies to the misrepresented 
address, and other attacks that conceal the source of 
the attacks). The correspondence between source IP 
addresses and access lines can also be managed so 
that a source IP address can be investigated upon the 
detection of attack-like packets and the originating 
access lines of the attacking packets can be deter-
mined.
(3) Protection of SIP-controlled communications
The NGN provides a particularly robust defense 
function for SIP-controlled session-based communi-
cations that have quality and reliability requirements. 
Specifically, the NGN uses an NBE-equivalent func-
Special Feature: NGN Focus
Network equipment 
not always controlled by NGN provider
Terminal
border 
elements
Provider-
controlled 
equipment
NGN network
elements
NBEs
Terminal
border
elements
Terminal
equipment
Terminal
equipment
Terminal
equipment
Terminal
equipment
Untrusted zone
Trusted but 
vulnerable zone
Trusted zone
Network elements 
controlled by NGN provider
Fig. 1. NGN security trust model (ITU-T Y.2701).
Table 1. Main security requirements in Y.2701.
Eight dimensions of ITU-T X.805
(1) Access control
(2) Authentication
(3) Non-repudiation
(4) Data confidentiality
(5) Communication security
(6) Data integrity
(7) Availability
(8) Privacy
Main security requirements for NGN providers in Y.2701
• Restrict access to authorized subscribers.
• Able to authenticate subscribers, equipment, network elements, and other networks.
• Not specified
• Provide a mechanism for preventing the interception of information. 
• Able to prevent communications with a non-compliant user terminal to mitigate DoS attacks and the
spread of viruses.
• Provide disaster-recovery functions and procedures.
• Protect the subscriber’s private information such as location data, IDs, phone numbers, and call-acco-
unting information.
DoS: denial of service
ID: 
identity
• Protect the integrity of subscriber traffic by cryptographic or other means.
• Protect the integrity of control messages by cryptographic or other means.
• Protect the integrity of management traffic by cryptographic or other means.
• Protect the confidentiality of subscriber traffic by cryptographic or other means. 
• Protect the confidentiality of control messages by cryptographic or other means.
• Protect the confidentiality of management traffic by cryptographic or other means.

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